#include <iostream>

using namespace std;
int jia_fa(int n)
{
	if(n != 0)
	return n + jia_fa(n-1);
	else
	return 0;
}
int main()
{
	int n = 0;
	cin >> n;
	int sum = jia_fa(n);
	cout << sum ;
	
	return 0;
}
